A computer determines an optimal route to a destination. The computer identifies the present position of a navigation device with a user selecting a destination. The computer acquires current information comprising road, business hour, traffic congestion patterns, a plurality of conveyance modes, and time buffer information relative to the present position and the selected destination to store in the memory. A route identification unit identifies, from the acquired current information, an optimal route from the current position to the selected destination. The computer stores the acquired information in the memory of the navigation device and identifies an optimal route from the current position to the selected destination.